But a slew of complaints has gotten the attention of U.S. law enforcement and the crackdown has begun.

While the primary target are Chinese and Koreans living in the States due to the large numbers participating in the scam, the practice is growing increasingly popular with Nigerian, Taiwanese and Turkish nationals according to one study.

Mexicans living and working in the States under work visas are also known to widely take advantage of the American Constitution’s 14th Amendment, which grants any child born on U.S. soil automatic citizenship. When those children turn 21 they then qualify for the “family reunification” statute which allows their family to petition for permanent residence –which most often is granted.

Just a few weeks back a Chinese-run mansion subdivided into 17 bedrooms and 17 bathrooms, was shut down for code enforcement violations –at the moment the only legal recourse available to authorities.

In 2010, the mothers of 7,719 children born in the United States reported that they lived overseas, according to the National Center for Health Statistics – a figure up nearly 55 percent since 2000.

Critics say the data vastly understate the number, because they use information self-reported by parents during their hospital stays.

Pregnant women are driven to make the long and risky trip because of educational and job opportunities in the United States, Chang said. Some hope their children can help them emigrate later; once the children turn 21, they can petition the government to grant legal residency for their parents.

The trend is on the rise, Chang said, adding that there are more than 40 maternity operations that host 1,000 women in the Los Angeles area alone.

The United States and Canada are the last two developed countries that grant birthright citizenship. The United Kingdom phased out the policy in 1983, while Ireland did so in 2005 through a referendum.